Refrigeration systems, including mobile units and stationary units, require servicing from time to time. Refrigeration system servicing often involves the introduction of a fluorescent, leak detection dye into the system. Servicing similarly can involve the introduction of a liquid compressor lubricant, e.g., a mineral oil, a polyol ester, or a polyalkylene glycol. These liquids are introduced into refrigerant systems by means of devices commonly called "dye injectors" (or "oil injectors"). Although various dye injectors have been used, they can be generally classified into two types, i.e., flush-through-type and injection-type.
The feature that distinguishes conventional flush-through injectors is that refrigerant flow supplies the force that moves (flushes) the liquid dye from the injector into the refrigeration system. Conventional flush-through injectors are single-application devices. This means that the injector must be opened and refilled with dye, for each dose of dye injected. An additional limitation is that the dose per injection is fixed at the capacity of the dye chamber, which must be filled completely, to avoid introducing air into the refrigeration system.
The feature that distinguishes conventional injector-type devices is that the concentrated liquid dye is displaced from the injector by a mechanical pushing mechanism, instead of refrigerant flow. In other words, the fluid does not flow through the injector. This type of design is analogous to a caulking gun or a drug syringe. Conventional injectors allows multiple injections. However, unless the injector output hose remains filled with dye, it must be purged of air each time the injector is connected to a refrigeration system. With this type of device, a small amount of dye often remains at the point of attachment between the injector and the refrigeration system.